Core B, the Clinical Core will support Projects 1-4. The goals of this project are to prospectively enroll randomly selected men attending an STD Clinic and their regular sex partners. These men and women will be followed prospectively to provide well characterized clinical specimens coupled to a detailed behavioral, historical, and demographic database. As part of the clinical core evaluation, all men and women will be cultured at each visit for Neisseria gonorrhoeae and Chlamydia trachomatis. All women will be cultured for Trichomonas vaginalis as well. In addition, specific specimens to be utilized for more specialized microbiologic tests will be provided to the investigators in Project l and 2 while chlamydial isolates, local secretions, and sera will be provided to Dr. Morrison for the immunologic studies outlined in Project 4. All male participants will be eligible to participate in Project 4, a randomized clinical trial of a targeted intervention to reduce recurrent urethritis in men. Finally, a major goal of the Clinical Core is to develop a specimen repository comprised of microbial isolates from patients with STDs, genitourinary specimens, genital secretions, other mucosal secretions, and sera, all of which are linked to a comprehensive database. These data will be useful resources for addressing new questions which arise in the course of the CRC grant, as well as to explore new hypotheses that are generated with passing time. The Clinical Core of the UAB STD CRC provides a very efficient coordinated mechanism for cost effectively providing investigators with specimens and appropriate clinical data to address the wide variety of specific aims outlined in Projects 1-4.